Having known people who went to private school, and discussing the differences between public and private schools, one of the biggest differences is the balance of power of the administrators and teachers. Getting kicked out of private school, especially ones that take a terms of service like approach in their legal language and contracts, means that on average students show a lot of respect to their teachers and to administrators. The private schools my friends went to all generally had a policy of having to refer to staff as sir/ma'am, had very strict codes of conduct, and generally acted quickly to kick trouble makers out of the school.